Track shunting apparatus



B. E. o HAGAN TRACK SHUNTING APPARATUS j Oct. 13, 1936.

Filed June 16, 1933- INVENZ'OR fimnand EOZ/agazz BY QJKW HIS ATTORNEYPatented Oct. 13, 1936 UNITED STATES PATENT OFFICE 2,057,159". I TRACKSHUNTING A PPARA TUS Bernard E. OHagan, Swissvale, .Pa., assignor to TheUnionSwitch & Signal Company, Swissvale, Pa., a corporation ofPennsylvania Application June is, 1933,- Serial No. 676,025

2 Claims. (o1. '246-34) My invention relates to track shunting apparatusof the type involving means carried on a vehicle for applying apotential to the rail surface for disrupting the resistance film formedon 5 such surface and thereby decreasing the rail contact resistance.

The present invention is an improvement on the apparatus described andclaimed in an application for Letters Patent of .the. United States,Serial No. 644,180, filed by me on November 25, 1932, for Track shuntingapparatus.

One object of my invention is the provision of means for increasing theopen circuit secondary voltage of the transformer which applies po- 15tential to the rail surface, without increasing the short circuitsecondary current beyond the desired amount.

I will described one form of track shunting apparatus embodying myinvention, and will 20 then point out the novel features thereof inclaims.

In the accompanying drawing, Fig. 1 is a diagrammatic view showing oneform of track shunting apparatus embodying my invention.

25 Fig. 2 is a vector diagram illustrating the electricalcharacteristics of the apparatus shown in Fig. 1.

Referring first to Fig. 1 of the drawing, the reference characters R andR. designate the 0 track rails of a stretch of railway track, whichrails are divided by insulated joints to form a section D-E. Thissection is provided with a track circuit including a track relay Fconnected across the rails at one end of the section, 35 and atransformer H the secondary of which is connected across the rails atthe other end of the section through a current-limiting impedance 5. Theprimary of transformer H is constantly supplied with alternating currentfrom a 4,0 suitable source, the terminals of which are designated Y andZ.

The remaining apparatus illustrated in Fig. 1 is arranged to be carriedon a rail vehicle. The reference character MG designates a motor gen- 45erator set comprising an alternating current generator G driven by amotor M which receives current from a battery B. A transformer T has aprimary winding P supplied with current from the generator G, and twosecondary windings 50 S and S having substantially the same number ofturns. Winding S is connected across the two rails of the track by meansof suitable contact shoes I and 4, whereas winding S is connected acrossthe rails by means of contact 55 shoes 3 and 2. The polarities of thetwo secondary windings are so chosen that the voltages of thesewindingswill be series-aiding and will be efiective to cause current to flowover the following path: from the upper terminal of secondary S throughshoe I, rail R shoe 2, secondary S shoe 3, rail R. and shoe 4, to thelower terminal of secondary S Consequently, the voltages of bothwindings S and S will be effective to break .downany resistance filmwhich may exist between the contact shoes and the rails. ,Interposedbetween the generator G and the trans-former primary P, is a reactor X,the. purpose of which is to limit the, maximum film break-down currentwhich can flow, in order to economize the output of generator G, and,consequently, to limit the drain on the battery B. That is to say, thecombination of transformer T and reactor X is such that with thesecondary windings S and S on short circuit, the amount of current whichwill flow through the secondary circuit is determined by the impedanceof the reactor X and the ratio of turns between the primary P and thesecondaries S and S If an attempt is made to increase the open circuitsecondary voltage of transformer T by decreasing the ratio of turnsbetween the primary and the secondaries, the amount of current whichwill flow through the short circuited secondary windings will bedecreased since it is proportional to the turn ratio. The importantfeature of my invention is the provision or means for increasing theopen circuit secondary voltage available to break down the rail film,without changing the amount of short circuit current which will flowafter the film has been broken down, and I accomplish this result byconnecting a condenser C in multiple with the primary of transformer T.By means of this condenser, it is possible to increase the open circuitsecondary voltage for a given ratio of transformer turns, with theresult that a high voltage is available for breaking down the filmwithout increasing the short circuit secondary current beyond thedesired amount.

Referring to the vector diagram in Fig. 2, EP represents the voltageacross the primary of transformer T with the secondaries on opencircuit. IM is the magnetizing current of the transformer T for thisvoltage, and I0 is the current taken by the condenser C, making a totalcurrent of IT flowing from the generator G. The total current IT produces a voltage drop across reactor X, which is shown as Ex, and thetotal generator voltage is Ea, which, as will be seen, is very muchsmaller than voltage across the primary of the transformer is reduced toa very small value, with the result that the current'rtaken by thecondenser C is negligible in comparison to the load current. The

current then flowing in the short circuited sec- .ondaries' isdetermined solely byrthe amount of primary current, and this in turn isdetermined by the value of reactor X, the generator voltage, and theratio of turns between the primary P and the secondaries S and S Q a'The apparatus shown in Fig. 1 may be modified by omitting the reactor Xand replacing this re- 7 actor by a condenser so proportioned as tobalance the inherent reactance of transformer T. This modificationrequires one less piece of apparatus, but the condenser would have to beof considerably higher capacity than with the arrangement shown inFig. 1. v The present application is closely related to my copendingapplication for Track shunting apparatus, Serial No. 678,629, filed July1, 1933, which latter application contains claims which cover broadlycertain features of the invention disclosed in myrpresent application. a

; Although I have herein shown and described only one form of apparatusembodying my invention, it is understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a stretch of railway track and a rail vehicletravelling thereon, a transformer on the vehicle having a secondaryconnected with a rail surface for disrupting the resistance film foundon such surface, a circuit for the primary 0! said transformer includinga source 7 of current and a reactor, and a condenser connected inmultiple with said primary for increasing the open circuit voltage ofsaid secondary whereby the voltage available for disrupting thetransformer on the vehicle having two secondaries each of which isconnected across the two rails of the track, the instantaneous relativepolarities of said connections with either rail being opposite-so thatthe voltagesof said two secondaries will aid each other in breaking downthe :rail contact re sistance, a circuit for the primary of saidtransformerincluding a source of current and a reactor, and a condenserconnected in multiple with said primary for increasing the open circuitvoltage of said secondary whereby the voltage available fordisrupting'the film is increased-without changing the amount of shortcircuit current which will flow after the film has been broken downBERNARD E. OHAGAN.

